Combustion apparatus



' March 1939- D. J. MOSSHART COMBUSTION APPARATUS V M i Filed Jan. '4, 1938 3 1 x m .3. & -3 mw J 3%. 2w n. v 8 r M. nil ..r. v hay/4&2. MN

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. h" U s; on H v INVENTOR [Jo/mu J. M ss mm v -fbldk ,7,, ATTORNEY 1 Patented Mar. 7, 1939 UNITED STATES PATENT OFFl E COMBUSTION APPARATUS Pennsylvania Application January 4, 1938, Serial No. 183,266

2 Claims.

My invention relates to grates for progressive feed stokers of the type disclosed in the patent to Foresman et 3.1., 1,683,341, September 4, 1928, and to Foresman 1,806,554, May 19, 1931, and it has for an object toimprove the grate bars from the point of view of durability thereof.

In the use of stokers of the above character, shortness of life of the grate bars is occasionally experienced due to excessive heating or burning. When the ash content of the fuel is low there is but little ash available to insulate the grates from the heat of the burning fuel, and the principal protection ofthe grates from overheating must be obtained by cooling them with the combustion air. Such ash as is present may fuse to the grate bar if the latter becomes overheated. When ash or clinker fuses adjacent to the top surface of a bar, not only may'the fusing mass stick or adhere to the bar, but the normal travel of the bed along the bars will be disturbed and air flow between adjacent bars will be impeded or rendered irregular, with the result that at least the upper portion of the bars may be burned or fused. Normally, with air entering the bottom of the fuel bed through the spaces between adjacent bars, suchair not only exerts a cooling effect on the bars but also on the portion of the bed immediately adjacent thereto, this effect being accomplished by the action of the bars in transmitting heat from the bed to the entering air and directly by the air as the latter initially enters the bed, with the result that the temperature of the region at the tops of the bars is kept below the fusion point. On the other hand, where the ash has a relativelylow fusion temperature, the cooling effect of air may not be sufficient to prevent fusion at the fuel supporting surface of the bars with the result that the fusing mass of ash and clinker may adhere to the bars, impede the entrance of 'air, and bring about excessive temperatures of the bars and burning thereof. Accordingly, I have improved the bars from the point of View of heat transfer therefrom to the air so that, even though ash of low fusion temperature should be in contact with the bars, fusion thereof and'consequent adhesion to the bars is prevented and regular flow of air to the fuel bed is maintained in consequence of which burning and fusing of the bars themselves is avoided.

A more particular object of my invention is to provide a grate for a progressive-feed stoker having a plurality of sections linked together in end-to-end relation in the direction of fuel bed travel, each section having a plurality ofv grate bars arranged in parallel side-by-side relation and each bar having integral, short, pin-like projections extending from one face thereof, the projections serving to provide adequate surface for transferring heat from the bars to the air so that the temperature of the portion of the bed, particularly adjacent to the top surface of the bars, may be kept below the fusion point, whereby normal travel of the bed along the grate may be preserved and fusion or burning ofthe bars may be avoided.

These and other objects are effected by my invention as will be apparent from the following description taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a transverse sectional view of a stoker whose grates embody my improved bars;

Fig. 2 is a side elevational view of one of the grate bars but drawn to a larger scale;

Fig. 3 is a sectional view taken along the line III-III of Fig. 2 and viewed in the direction of the arrows;

Fig. 4 is a sectional view taken along the line IVIV of Fig. 2 and viewed in the direction of the arrows; and,

Fig. 5 shows a plurality of grate ba'rs assembled in side-by-side, parallel relation.

Referring now to the drawing more in detail, in Fig. 1, there is shown a retort I ll supplied with fuel in the usual way by the ram construction indicated generally, at H, fuel filling the retort and overflowing from the sides thereof onto the overfeed grates, at l2, l2, combustion being substantially completed on the latter and ash and are of the link-grate type to effect travel and 1" agitation of the fuel bed therealong toward the ash discharge device or devices. Where the linkgrate, overfeed section is applied to a multipleretort underfeed stoker, as disclosed in the aforesaid patent to Foresman 1,806,554, operation of the overfeed section is substantially the same. Accordingly, while I show my improved grate bars embodied in overfeed link grates of a stoker of the single retort type; it is to be understood that my improvement is applicable to overfeed link grates irrespective of the type of stoker to which applied.

The retort l and the overfeed grate sections, at I2, l2, support the fuel bed, air for combustion being supplied from the plenum chamber, at I4, to the fuel bed through the spaces between adjacent bars.

Each overfeed grate, at l2, includes a plurality of sections, at l5, l6, l1, and I8, adjacent ends of the sections being pivotally connected to gether at I9, 29, and 2|, the initial section, at l5, being pivotally supported at 22, at the top edge of the retort and the final section, at l8, being arranged for reciprocatory and oscillatory movement, the sections of the grate being moved so that the grate as a whole has an undulatory or wave-like motion securing progressive movement of the bed and agitation thereof, as disclosedv in the patents aforesaid.

With grate arrangements of this type, the bars occasionally burn or become fused where the fuel used has a sufficiently low ash-fusion temperature, for example, fuels containing iron. or sulphur, in which case, the ash may fuse immediately adjacent to the bars and adhere to the latter, or fused ash and clinker may trickle down and adhere to the bars, thereby impeding the normal flow of air between the bars and consequently promoting overheating and burning or fusion of the bars. In accordance with the present invention, the bars are constructed and arranged for more effective transfer of heat from the bars to the air so that the temperature of the bars and of the portion of the fuel bed immediately adjacent thereto may be kept at a point below the ash-fusion temperature, with the result that burning or fusion of the bars is avoided even though they are used in connection with fuel whose ash fusion point is relatively low or which has a tendency to form clinkers adhering to the bars.

While Figs. 2, 3, 4, and 5 show bars 24 of the first section, at IE, it will be understood that the application of my invention exhibited by these views is identical with respect to the bars of the remaining sections at l5, l1 and I8.

As shown in Fig. 3, each bar 24 is generally of a rectangular section whose depth is substantially greater than its width, the bar having side faces 25 and 26 and a top face 21.

The side face 25 has, integral with and springing therefrom, an uppermost row of projections 28, and a plurality of rows of pin-like projections 29, the projections of adjacent rows being preferably staggered.

The uppermost projections 28 have their top surfaces 39 forming continuations of the upper bar surface 21 and the projections 29 are made sufficiently longer so that, when the bars are assembled, the outer ends of the latter projections will be spaced from the adjacent face 25, whereby there will be adequate air admission area with the transverse dimensions thereof kept small enough to prevent excessive sifting between the bars.

Each side face 26 preferably has depressions 32 formed therein and aligned with the projections 29, the depressions of one bar receiving the projections of an adjacent bar when the bars are assembled to form a grate section. This arrangement assures that the projections 29 may extend entirely across the space 33 between adjacent bars even though there should be varia. tion in projection length, planar relation of the face 26, or warpage. of a bar, with the result that the air is compelled to sweep effectively the surfaces of the projections.

In addition to the uppermost projections 28 cooperating with the adjacent bar face 26 to define a suitable air admission area, the upper faces of such projections constitute parts of the fuelcontacting surface and, therefore, constitute additional surface for absorbing heat from the fuel bed. The heat so absorbed is transmitted through the metal of the bar and transferred from the side surfaces '25 and 26, from the surfaces of the projections 29 and from the surfaces of the depressions to the air passing through the spaces 33. Not only are the projections 29 sufficiently numerous to provide the desired additional heat transfer surface, but the staggered arrangement thereof assures of such a tortuous and turbulent condition of the air in. the spaces 33 that highly effective contact of the air with such surface is secured.

As shown, the projections 29 are preferably frusto-conical and the outer ends are sufficiently smaller than the depressions 32 so as to enter the latter freely with sufficiently large tolerance to facilitate manufacture and assembly. Improved heat flow to the surfaces of the projections is secured and the turbulent air is given some bias toward the adjacent face 26 with the result that the latter, the depressions 32, and the smaller ends of the projections in the latter are effectively swept by'air to minimize the accumulation of debris between the projections and the depressions and to promote transfer of heat from the surfaces of the latter to the air.

The projections 29 of each row are preferably joined by ribs 34 thereby providing row structures springing laterally from at least one face of each bar toward the face of the adjacent bar and serving, not only to provide additional heat transfer surface and transferring heat from the bar to the air passing between adjacent bars, but also to provide a multiplicity of orifices or restricted flow areas 35 between adjacent bars. The projections and the ribs promote turbulence of the air as well as serve to transmit heat thereto, this result being promoted by the staggered relation of projections in adjacent rows. The series of orifices or restricted fiow areas in the flow path between adjacent bars, in addition to promoting a turbulent flow condition, assures of more uniform flow of air even though the fuel bed conditions should vary. For example, if the fuel bed resistance at the region supplied by the space between a pair of bars should be different from that of another space, this difference tends to be compensated for by the restrictive or throttling effect of the orifices. The row structures comprised by the projections and the ribs joined thereto also add to the mechanical strength of the bar.

Where the grate bars are arranged to engage pivot pins directly, they are preferably provided with terminal cars 36 having pivot pin openings 31.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What I claim is:

1. A grate bar having a section whose depth is substantially greater than its width; having an upper fuel supporting surface; having one face provided with a plurality of spaced and substantially parallel row structures springing therefrom and adapted to extend toward the adjacent lateral face of an adjacent bar to transfer heat to air passing between the bars, each row structure including a series of projections joined by ribs arranged between adjacent projections and the ribs of the row structures providing a plurality of orifices or restricted flow areas in the flow path between adjacent bars; and having the other face provided with depressions aligned with and larger than the outer ends of the projections.

2. A grate bar having a section whose-depth is substantially greater than its width; having an upper fuel supporting surface; having one side face provided with a plurality of pin-like projections springing therefrom and adapted to extend toward the adjacent side face of an adjacent bar totransier heat to air passing between the bars, said projections being spaced both lengthwise and transversely of the side face; and having the other side face provided with depressions aligned with and larger than the outer ends of the projections.

DONALD J. MOSSHART. 

